Apparatus for contacting solid and gaseous materials



April 1933- E. o. BARSTOW ET. AL 1,905,883

APPARATUS FOR CONTACTING SOLID AND GASEOUS MATERIALS Filed Feb. 1930 6Sheets-Sheet 1 erted M 1 6' Inverfer) Chqme i B FIWIA Hun/8 6 INVENTORSBY 5mm 6M JW 9W ATTORNEY April 1933- E. o. BARSTOW ET AL 1,905,883

APPARATUS FOR CONTACTING SOLID AND GASEOUS MATERIALS Filed Feb. 13, 1930s Sheets-Sheet 2 mam/1,3

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INVENTORS xm'm Q @wwtW/ u BY 5mm 6. M

fio'mad ATTORNEY April 1933- E. o BARSTOW ET AL 1,905,883

APPARATUS FOR CONTACTING SOLID AND GASEOUS MATERIALS Filed Feb. 13. 19506 Sheets-Sheet 5 Fig.3

INVENTORS ATTORNEY v April 1933- E. o. BARSTOW ET AL APPARATUS FORCONTACTING SOLID AND GASEOUS MATERIALS 6 Sheets-Sheet 4 Filed Feb. 131930 Preheat; ZZ

Fig.4 INVENTORS 6m (9. @Wmw BY 5% Jim/w wmnfd ATTORNEY April 25, 1933.E. o. BARSTOW El AL APPARATUS FOR CONTACTING SOLID AND GASEOUS MATERIALSFiled Feb. 15} 1950 6 Sheets-Sheet 6 INVENTORS elm 2mm ATTORNEY Fig. 6

Patented Apr. 25, 1933 UNITED STATES PATENT OFFICE EDWIN O. BARSTOW ANDSHELDON B. HEATH, OF MIDLAND, MICHIGAN, ASSIGNORS TO THE DOW CHEMICALCOMPANY, OF M MICHIGAN IDLAND, MICHIGAN, A CORPORATION OF APPARATUS FORCONTACTING SOLID AND GASEOUS MATERIALS Application filed February 13,1930. Serial a... 428,086.

The present invention has reference to methods and apparatus forcontacting solid and gaseous materials wherein a body of solid materialin divided or comminuted form must be maintained at a temperatureranging from ordinary temperature to a moderately elevated temperaturewholly or to a large degree by the application of external heating orcooling while subjecting the same to the action of a gas. In aco-pending application Ser. No. 428,065, filed Feb. 13, 1930, now PatentNo. 1,852,227 we have claimed the method hereinafter described, Thepresent application is directed specifically to apparatus adapted forcarrying out such method.

An object of the invention is to secure a uniform distribution of theexternal heat supplied or abstracted throughout the body of solidmaterial by passin streams of heated or cooled aeriform gases through aplurality of tubes or conduits distributed within said body. A furtherobject is to provide for a uniform distribution of the gas throughoutthe body of solid material by introducing the same thereinto through aplurality of outlets disposed within said body. Another object is topreheat or precool the gas approximately to the desired temperaturebefore contacting the same with the body of solid material, suchpreheating or precooling being efiectecl through the agency of the samemedium that is employed for heating or cooling the solid material. Stillanother object is to conserve the heat content-of the heating gases,where such are employed, by constantly recirculating the same and addingthereto only such increment of heat as required to compensate for theheat expendedin maintaining the temperature of the reacting materialsand in losses. A design is also provided for a special type of apparatusadapted to the carrying out of the method under the conditions hereinset forth. These and other objects and advantages will appear from theannexed drawings and following description, setting forth in detailseveral of the various ways in which the principle of the invention maybe used.

In said annexed drawings Fig. 1 is a vertical cross-section through achamber adapted for simultaneously heating or cooling a body of solidmaterial and intimately contacting a gas therewith. Fig. 2 is ahorizontal section on the line BB and Fig. 3 a vertical cross-section onthe line A-A of Fig. 1. Fig. 4 shows a superposed duplex arrangementof'two chamber units together with gas-line connections therefor. Fig. 5is a vertical section of an assembly including a reaction chambertogether with circulating means for distributing heating gases and afurnace for supplying the same, all enclosed within a single housing.Fig. 6 shows in perspective a general assembly of the apparatus, withsections broken away to bring out details of interior arrangement.

The invention is particularly applicable for reactions or operationswherein hydrochloric acid gas is contacted with a solid material :individed form at a suitably elevated temperature. More particularly is itadapted for dehydrating magnesium chloride in an atmosphere or currentof hydrochloric acid gas. The detailed description hereinafter providedsets forth such lastnamed application specifically, but the same is tobe regarded equally as an illustrative example showing the broadprinciple underlying the invention.

Referring to the drawings, in Figs. 1, 2 and 3 a dryer or reactorchamber 1 is shown, having lateral walls parallel in mid-section butconverging at the upper and lower ends thereof, the whole being borne bysupporting members 2. The end walls 3, conform.- ing in sha e to thecross-sectional view shown in Fig. 1, constitute tube sheets'into whichare welded a plurality of tubes or flues 4 extendin lengthwise ofchamber 1, the ends thereo being left open. Tubes 4 are preferablyarranged in banks or rows uniformly spaced apart, the spacing of thetubes preferably being approximately equal to the tube radius, orgenerally not exceeding the diameter of the tubes. Extendingtransversely of chamber 1 and secured to the lateral walls thereofbetween alternate banks of tubes are gas distributors 5 and 5a in theform of inverted troughs, likewise equally spaced in rows, and openingdownwardly into the space within chamber 1. The rows of troughs 5 and 5aare alternately arranged, the former terminating in headers 6 at oneside of-chamber 1 and extending lengthwise thereof, and the latterterminating in similar headers 7 at the opposite side. Headers 6 areconnected by laterals 8 with manifold 10 centrally located at one sideof chamber 1, and headers 7 are connected by laterals 9 with twocommunicating manifolds 11 located at each end of the opposite side ofchamber 1. A charging inlet 12 leads through a tapered passage 13 intoa. hopper 14 extending the full length of chamber 1 and communicatingtherewith through gate 15. A tapered discharge chute 16 leads from thebottom of chamber 1 to outlet 17 controlled by valve 18.

Fig. 4 shows diagrammatically a. preferred apparatus arrangementconsisting of two umts of the type illustrated in Figs. 1-3, one beingsuperimposed upon the other. Such arrangement involves a modified layoutof piping for connecting between the two separate units. Hence,employing like reference characters forlike apparatus elements as inFigs. 1-3, 1 and 1 are the dr er chambers similarly provided with tulies4 and 4, inverted troughs or distributors 5 and 5, and headers 6 and 6',the latter connected b pi es 8 and 8' to manifolds 10 and 10'. ea ers 7and 7 are likewise disposed in identical fashion as in Fig. 1, but areinterconnected here by means of pipes 19, such connection beingadvantageously made between oppositely located pairs of headers asshown. Feed inlet 12,

' passage 13, hopper 14 and gate 15 are provided as before, while theopening between chambers 1 and 1' is controlled by gate 20. Outlet 17serves for bottom discharge from the apparatus. Manifold 10 is connectedby pipe 21 with a, preheater 22, which may be in the form of a tubularheat exchanger, the inlet to which is pipe 23 in turn.connected to theblower as shown. Similarly pipe 24 connects manifold 10 with cooler 25of similar form and having an outlet pipe 26 connected to an exhauster.

The apparatus shown in Figs. l4 is to be enclosed within aheat-insulated housing which is illustrated diagrammatically 1n formheating of the entire charge.

Fig. 5. In said Fig. 5 housing 27 is divided into two parts byhorizontal partition 28. In the upper part thereof is placed dryer 1,which may be either a single or double unit, leaving a fore-compartment29 and an aftercompartment 30 communication between which is establishedthrough tubes or fines 4, such compartments being separated from eachother in the space at either side of chamber 1 by cross-walls orpartitions indicated by dotted lines at 39. In the lower part of housing27 is placed a fan or blower 31 which draws from compartment 30 throughopening 32 and duct 33 and discharges into compartment 29 throughopening 34. A furnace 35, suitably equipped for the combustion or solid,liquid or gaseous fuel (here shown for using solid fuel) is likewiseincluded within housing 27, the products of combustion passing throughfine 36 directly into compartment 30, and from the latter a vent 37 isprovided. 'Inlet 12 to dryer 1 extends above the top of housing 27,while discharge outlet 17 is connected to a suitable conveyer (not shownfor removal of finished prdouct outside of housing 27. Preheater 22 ispreferably located within housing '27, and cooler 25 may likewise beplaced therein but separated from the other apparatus by an innerpartition indicated by dotted line 38.

In Fig. 4 housing 27 and partition 38 are indicated by the dotted lines.A general assembly of the herein described apparatus, viewed from thefurnace end of the casing, is represented in Fig. 6. The relativeaprangement of parts in the complete apparatus will be readily apparenttherefrom. Interior details, shown partly in the broken away sectionsand partly by dotted lines, correspond to features more particularlyillustrated in Figs. 1-5, and are indicated by like reference numerals.

For operating the apparatus just described, -chamber 1 is completelyfilled in the spaces surrounding the flues 4 with the solid material individed form, e. g. partially dehydrated magnesium chloride containingfrom 1 to 2 molecules of water of crystallization, such material beingcharged through inlet 12 in quantity sufficient at least partially tofill hopper 14 in addition to filling chamber 1 completely. The excessmaterial in hopper 14 may be fed down into chamber 1 as the processcontinues to make up for shrinkage in the charge. The charge is heatedto the desired treating temperature by passing hot combustion gasesthrough fiues 4, the disposition of the fines permitting a rapid andsubstantially uni- The gas to be reacted or contacted with the solidmaterial, e. g. dry hydrochloric acid gas, is admitted through manifold10 an'd laterals 8 into headers 6, and thence into inverted distributingtroughs 5 whence it passes into the charge of solid material andpermeates the mass thereof by diffusion. Laterals 8 are advantageouslyprovided with adjustable orifices 40, as indicated in Fig. 1 toproportion the volume of gas flow therethrough to the cross-section ofthe chamber 1 at the point of entry and hence to the volume of the spaceto be filled with gas from each orifice. By means of the arrangementshown the gas is introduced and distributed practically simultaneouslyand at a uniform rate throughout the mass of the charge, thus securingan exceptionally intimate contact therebetween under substantiallyidentical conditions at all points. The headers 7 for collecting thespent gases I are fed by means of similar inverted troughs 5a. Headers 6and 7 are ranged on opposite sides of chamber 1 in uniformly staggeredrelation, thereby establishing conditions for introducing andwithdrawing gases as nearly as may be at the same rate and volume in allparts of chamber 1. The spent gases collected in headers 7 are drawn oflthrough laterals 9 into manifolds 11, and thence removed from thesystem. When the charge is finished, the dry, solid material isdischarged by gravity through outlet 17 by opening valve 18, and whenemptied a new charge may be fed in and the operation repeated.

When the duplex arrangement shown in Fig. 4 is employed the process iscarried out in twostages with gravity feed of materials from the firststage to the second. An advantage of such arrangement is that thereaction time may be doubled without loss of output, while the charge isthoroughly mixed once during the process when it is being transferredfrom the upper to the lower chamber. The material is charged in at inlet12 inamount to fill chamber 1, gate 15 being open and gate 20 closed,and the reaction started. When the reaction has been carried to anydesired point, the charge in chamber 1' is discharged into chamber 1 byopening gate 20, the material being thoroughly turned over and mixed inthe operation, and a fresh charge is admitted intocha'mber 1. Thegaseous reaction component is introduced through pipe 23, passes throughpreheater 22 and is delivered into chamber 1 by ,means of pipe 21,manifold 10, laterals 8, headers 6 and distributers.5. The gases fromchamber 1 are collected in headers 7 and conveyed thence via pipes 19 toheaders 7 of chamber 1, whence they are dis-- tributed throughout thecharge therein through inverted troughs 5' and finallytaken off throughheaders 6', laterals 8' and manifold 10. The exit gasesfmaythen bepassed through pipe 24 to cooler 25 and thence discharged through pipe26. If desired, the direction of travel of the gas duct 33 by fan 31 anddelivered into compartment 29 through opening 34. The hot gases thentraverse tubes 4, giving up heat to the materialof the charge, andissuing into compartment 30 again are in part recirculated and in partescape through stack 37.

The capacity of the fan 31 is made large in proportion to the volume ofthe entire system, thus providing for a large volume of flow at a lowvelocity. The volume of hot gases admitted at 36 and of used gases vented at 37 is controlled to maintain the desired temperature conditions;and the speed of fan 31 is regulated to'maintain the desired temperaturedrop through tubes 4, which, in general, is preferably held at about 5to 10 C. --By maintaining a low .temperature drop in the tubes, burningthe fuel with a minimum of excess air, recirculating the bulk of theheating gases and venting only a small amount, the heat of the gases iseffectively conserved and a nearly uniform temperature is provided atall points within chamber 1. The heating gases are likewise employed inpart for preheat- I ing the reaction-gases in preheater 22 so chamber 1at approximately the same temperature as that of the solid materialtherethat the latter gases are delivered to the in. When the entireapparatus assembly is enclosed within a single housing 27 suitablyprotected b heat insulating material the heat losses by radiation,leakage and from other causes are reduced to a minimum.

In the foregoing description a preferred arrangement of apparatus partshas been shown, but the invention is not limited spe cifically thereto.Various modifications in details will be suggested to those expert encedin carrying out operations related to those for which the presentapparatus is f designed and it is expressly understood that all suchdetailed modifications involving no materially altered mode of operationare comprehended within the scope of the present invention. For example,the flues 4" may be disposedzfverticallyinstead of horizon? tally;,fiues Ale-land distributing troughs 5 may be'arranged parallel to eachother, in.-

steadof transversely as shown; the regular spaeing'and alternatearrangement of suchi fiues and troughs may be variously modified,- a

and the nu ber-of the one relative tothe other may be changed in'diversways that will be readily apparent; equal spacing and regularalternation of fines and troughs, while being preferable, are notessential to the invention. The blower 31 may be located outside of themain casing, if desired, for greater accessibility in oiling, repairing,etc. without departing from the scope of the which it will volatilizematerially. The

cooler 25 shown in Fig. 4 is advisedly located in a separate compartmentwithin housing 27, so as to effect the cooling of the exit gases fromreaction temperature by regulated exchange ofheat with air or othermedium preferably at a temperature not lower than 140 C. such that thegases leave the cooler at or above the latter temperature. Suchpartially cooled gases may then be further cooled in contact withsurfaces of acid resisting materials, such as glass, stoneware, etc. thepreliminary cooling in contact with iron ha ing reduced thetemperatureto a point where the gas may be contacted with glass or similarapparatus without danger of cracking or otherwise damaging the same.

As already indicated, the herein described apparatus is particularlyadapted for dehydrating magnesium chloride in an atmosphere ofhydrochloric acid gas to form the anhydrous salt. The preliminarydehydration of normal hydrated magnesium chloride, MgCl .6H O, isconducted by drying in air, whereby a partially dehydrated productcontaining from 1 to 2 molecules of water of crystallization may beprepared with but aforesai preliminarily dried materials may then besubjected to further heating in an atmosphere of hydrochloric acid gasto drive off the remainder of the crystal water and convert theoxychloride or oxide to anhydrous magnesium chloride. In such latteroperation it is necessary for practically satisfactory results to securean intimate ingas, not only to effect the disengagement of water fromthe particles and the conversion of the oxychloride or oxide back tochloride, but also to facilitate the removal of the libs erated watervapor from the zone of drying. Such intimate intermixture of gaseous andsolid materials and the rapid removal of water vapor is achieved w1thconspicuous advantage by means of the improved method and arrangement ofapparatus just described. Furthermore the drying and reacting take placeunder more nearly uniform conditions than can be attained by other meansor methods.

The temperature for drying the partially dehydrated magnesium chloridemay be varied at will between the limits of 140 and 325 (1., alreadyreferred to, but the higher temperatures are preferred on account of themore rapid drying rate. In practice, therefore, the temperature of theheating gases entering the fines 4 of the dry-- er is maintained atapproximately 325 C. The rate of circulation of the heating gases ispreferably regulated so that the temperature drop through the fiues isabout 5 C. The hydrochloric acid gas introduced is preferably to besubstantially dry. In order for drying of the chloride to take placeunder the conditions given the water vapor content of the atmospherecontiguous thereto must be less than 17 per cent. by weight, and, ofcourse, the lower the water vapor content the more rapidly will theexplusion of water from the hydrated salt take place. Consequently wehave found it convenient to introduce the hydrochloric acid gas at suchrate that the issuinggases from the chamber have a water vapor contentof about 4 to 5 per cent, although we may maintain a somewhat slower ormore rapid gas flow provided that the water vapor content of-the issuinggases is held below 17 per cent. by weight. The charge of material isheld in the dryer under the conditions just stated until dehydration iscomplete, the actual time required depending upon the amount of thecharge,'the area of heating surface, and other factors.

The foregoing example illustrates one process wherein the principle ofthe invention and the apparatus described may be advantageouslyutilized. However, the invention is capable of wider application, and isnot limited to the specific example given. Other examples of processes'wherein a solid in comminuted form and a gas are contacted at ordinaryor at moderately elevated temperatures, e. g; up to about 400 C,. and towhich the'herein described apparatus may be readily adapted, are theremoval of gasoline from natural gas, or of benzine from coke-oven gas,by adsorption with activated charcoal; purifying coal gas from hydrogensulphide by contacting with ferric oxide or hydroxide; removing carbonbisulphide from coal gas by reacting with steam at about 230 C, inpresence of colloidal ferric hydroxide as catalyst. In such processesthe solid material may exercise quite diverse functions in variouscases, i. c. it may enter into the reaction with the gas, or it may actas an adsorbing medium, or it may serve as a catalyst, or in other waystake a necessary part in the reaction. The common feature present in allsuch processes such as are illustrated by the examples just given, isthat a gaseous material is intimately contacted with a solid material ina state of subdivision.

In the activated charcoal process for removing gasoline from naturalgas,the gas has been heretofore passed through a bed of the finelydivided charcoal at ordinary temperature until the charcoal has becomesaturated with the gasoline; then the saturated charcoal has beentreated directly with steam to carry off the gasoline vapors, which werecondensed and separated from the water. By employing an apparatusconstructed according to the present invention, the reaction chamber 1is filled with the charcoal, the gas to be scrubbed is admitted throughmanifold 10 and distributed within the body of adsorbent in the mannerpreviously described, while the exit gases pass out b way of manifold11, the process during t is stage being carried out at ordinarytemperature. When the absorption is complete, heating gases may bepassed through tubes 4 to heat the saturated charcoal to a sufficienttemperature to drive off the gasoline and leave the charcoal incondition to absorb a fresh charge of gasoline. Finally by suitablearrangement the revivified'charcoal bed may-be cooled by passing coldair through tubes 4, and the preceding operations repeated. By suchprocedure the direct steaming out of the charcoal and subsequentseparation of the gasoline and condensed water is supplanted by anindirect heating and cooling which avoids any such separation and whichis carried out under conditions to effect a rapid and efficient transferof heat throughout the charcoal body.

Similarly in purifying coal gas from hydrogen sulphide by passing thegas through or over beds of ferric oxide or hydroxide, the process isordinarily carried on until the absorbing material has become saturatedwith the iron sulphide formed so as to have lost its effectiveness. Theabsorbent is then revivified by exposing it to the air, whereby through,oxidation the iron sulphide is reconverted to the oxide with liberationof free sulphur. Considerable heat is developed in the oxidation, and

since it is imperative that the tem eratureof the mass be not allowed torise su ciently to melt the sulphur, it has been found necessary tocarry out the oxidation of the iron compound gradually at theexpenditure of considerable time. By adapting the apparatus of thepresent invention to such process, the chamber 1 would be filled withthe iron oxide absorbent, and the coal gas introduced into the bed ofabsorbent in the regular way, the purified gas passing out through theexit passages. When the absorbent became exhausted, the flow of gaswould be shut off and air introduced into the mass to effect thereoxidation, while the temperature of the oxidizing mass would becontrolled by passing cold air through tubes 4.

In the process for purifying coal gas from carbon bisulphide, reactor 1would be filled actant in granular or other divided form underconditions for effecting a uniform and rapid distribution of gasthroughout the body of solid material and also for maintaining a closeregulation of temperature therein either by heating or cooling or bothalternately. The apparatus described is adapted for use" at atmosphericpressure or under slightly increased or reduced pressure. All partsthereof, except the furnace and the heat 'insulatingwalls and partitionsof the housing, maybe constructed of iron or steel accordingto the usualmethods of fabrication and erection." The chamber 1 and .acces'sorypartsare preferably to be of welded construction throughout thus insuringpermanent gas-tightness and freedom from gas leakage. The tubes 4running lengthwise of the chamber and the troughs 5 and 50; ex-

tending crosswise thereof are firmly secured to the walls and formbraces and supports for holding the chamber walls rigid and preventingbulging or distorting. Such all metal construction permits rapidtransfer of heat between the charge of solid material and the heating orcooling gases in tubes 4, and'such heating or cooling may be assisted bypreheating or precooling the reaction gases before introducing the sameinto the reaction chamber. The arrangement of tubes 4 and distributingtroughs 5 and 5a.

reactant may be contacted with a, solid reage of heat to or from thesystem is largely prevented, and economy in construction is gained byavoiding the need for separately insulating the individual parts of thesystem.

Positive temperature control within the system may be maintained at alltimes by suit ably regulating the speed of the circulating fan, andcontrolling the quantity of heating or cooling gases supplied andvented.

Other modes of applying the princ ple of our invention may be employedinstead of the one explained, change being made as regards the means andthe steps herein dis-- closed, provided those stated by any of thefollowing claims or their equivalent be employed.

We therefore particularly point out and distinctly claim as ourinvention 1. In apparatus of the character described, the combination ofa closed rectangular chamber provided with a closable top charging inletand bottom discharge outlet, a plurality of horizontal flues: inuniformlyspaced relation extending lengthwise of said chamber and beingsecured in the end walls thereof, means for supplying a gaseoustemperature regulating medium to said flues. a plurality of horizontalinverted troughs dis posed transversely of said chamber and beingsecured to the lateral walls thereof in banks between alternate rows ofsaid flues, headers joining one end of said inverted troughs in eachalternate bank thereof and communicating with an inlet manifold, similarheaders joining the opposite ends of the inverted troughs in theremaining banks thereof and communicating with an outlet manifold andmeans for supplying a gas to said inlet manifold and for withdrawing agas from said outlet manifold.

2. In apparatus of the character described, the combination of a closedrectangular chamber provided with a closable top char ing inlet andbottom discharge outlet, said first chamber being superposed upon andcommunicating by means of said bottom discharge outlet with a secondchamber of similar form, each chamber containing a plurality ofhorizontal flues in uniformly spaced relation extending lengthwise ofthe chamber and be ng secured in the end walls thereof, means forsupplving a gaseous temperature regulating medium to said flues. aplurality of horizontal inverted troughs disposed transversely of eachchamber and secured to the lateral walls thereof in banks betweenalternate rows of said flues, headers joining one end of said invertedtroughs in each alternate bank thereof and communicating in each chamberwith amanifold, one such manifold serving as a gas inlet and the otheras a gas outlet, other headers joining end walls thereof, a plurality ofhorizontal inverted troughs disposed transversely of said chamber andbeing secured to the lateral walls thereof in banks betweenalternaterows of said flues, headers joining one endof said invertedtroughs in each alternate bank thereof and communicating with an inletmanifold, similar headers joining the opposite ends of the-invertedtroughs in the remaining banks thereof and communicating with an outletmanifold, means for supplying a gas to said inlet manifold and forwithdrawing a as from said outlet manifold, a heat insu ating housingenclosing said chamber and forming with the exterior walls thereofpassages leading to and from said flues and a blower adapted tocirculate a gaseous temperature regulating medium through said passagesand flues.

4. In apparatus of the character described, the combination of a closedrectangular chamber. provided with a closeable top charging inlet andbottom discharge outlet, said first chamber being superposed upon andcommunicating by means of said hottom discharge outlet with a secondchamber of similarform, each chamber continuing a plurality ofhorizontal flues in uniformly spaced relation extending lengthwise ofthe c amber and being secured in the end walls t other chamber, meansfor supplying a gas to said inlet manifold, means for withdrawing a gasfrom said outlet manifold, a heat insulating housing enclosing saidchambers and forming with the exterior walls thereof passages leading toand from said fiues and a blower adapted to circulate a gaseoustemperature regulating medium through said passages and fines.

5. In apparatus of the character described the combination of a closedrectangular chamber provided with a closablc top charging inlet andbottom discharge outlet, a plurality of fiues in uniformly spacedrelation extending lengthwise of the chamber and being secured in theend walls thereof, a plurality of horizontal inverted troughs disposedtransversely of said chamber and i being secured to the lateral wallsthereof in banks between alternate rows of said flues, headers joiningone end of said inverted troughs in each alternate bank thereof andcommunicating with an inlet manifold, similar headers joining theopposite ends of the inverted troughs in the remaining banks thereof andcommunicating with an outlet manifold, means for supplying a gas to saidinlet manifold and for withdrawing a gas from said outlet manifold, afurnace for supplying hot combustion gases to said fines, a heatinsulating housing enclosing said chamber and said furnace and formingwith the exterior walls thereof passages leading to and from said finesand a blower adapted to circulate'said combustion gases through saidpassages and fiues.

6. In apparatus of the character described, the combination of a closedrectangular chamber provided with a closable top charging inlet andbottom discharge outlet, said first chamber being superposed upon andcommunicatingby means of said bottom discharge outlet with a secondchamber of similar form, each chamber containing a plurality of fiues inuniformly spaced relation extending lengthwise of the chamber and being"secured in the end walls thereof, a plurality of horizontal invertedtroughs disposed transversely of each chamber and secured to the lateralwalls thereof in banks between alternate rows of said flues, headersjoining one end of said inverted troughs in each alternate bank thereofand communicating in each chamber with a manifold, one such manifoldserving as a gas inlet, and the other as a gas outlet, other headersjoining the opposite ends of the inverted troughs in the remaining banksthereof. each of such latter headers in one chamber communicating with asimilar header in the other chamber, means for supplying a gas to saidinlet manifold, means 'for withdrawing a gas from said outlet manifold,a furnace for supplying hot combustion gases to said flues, a heatinsulating housing enclosing said chambers and said furnace and formingwiththe exterior walls thereof. passages leading to and from said fluesand a blower adapted to circulate said combustion gases through saidpassages and fiues.

7. 1n apparatus of the character described, the combination of a closedrectangular chamber provided with a' clos'able top lengthwise of thechamber and'being securedin the end Walls thereof, a plurality ofhorizontal inverted troughs disposed transversely of said chamber andbeing secured to the lateral walls thereof in banks between alternaterows of said fines, headers joining one end of said inverted troughs ineach alternate bank thereof and communicating with an inlet manifold,similar headers joining the opposite ends of the inverted troughs in theremaining banks thereof and communicating with an outlet manifold, meansfor supplying a gas to said inlet manifold including a preheater forsuch gas, means for withdrawing a gas from said outlet manifold, afurnace for supplying hot combustion gases to said flues and saidpreheater, a heat insulating housing enclosing said chamber, saidfurnace and said prcheater and forming with the exterior walls of saidchamber passages leading to and from said flues and a blower adapted tocirculate said combustion gases through said passages and fines.

, 8. In apparatus of the character described, the combination of aclosed rectangular chamber provided with a closable top charging inletand bottom discharge outlet, said first chamber being superposed uponand communicating by means of said bottom discharge outlet with a secondchamber of similar form, each chamber containing a plurality of fluesdistributed with substantial uniformity throughout the space therein,the same extending lengthwise of the chamber and being secured in theend walls thereof, a

plurality of horizontal inverted troughs dis posed transversely of eachchamber and secured to the lateral walls thereof in banks betweenalternate rows of said fines, headers joining one end of said invertedtroughs in each alternate bank thereof and communicating in each chamberwith a manifold, one such manifold serving as a gas inlet, and the otheras a gas outlet, other headers joining the opposite ends of the invertedtroughs in the remaining banks thereof, each of such latter headers inone chamber communicating with a similar header in the other chain her,means for supplying ages to said inletmanifold, including a preheaterfor such gas, means for withdrawing a gas from said outlet manifold, afurnace for supplying hot combustion gases to said flues and said pre- 81,9o;sss

heater, a heat insulating housing enclosing said chambers, said furnaceand said preheater and forming with the exterior walls of said chamberpassages leading to and 5 from said flues and a blower adapted tocirculate said combustion gases through said passages and flues.

Signed by us this 8th day of February, 1930.

10 EDWIN O. BARSTOW. SHELDON B. HEATH.

